Wheel bearing apparatus that supports a vehicle wheel relative to a suspension apparatus incorporating a wheel speed detecting apparatus to detect rotational speed of the vehicle wheel to detect the wheel speed to control the anti-lock braking system (ABS) is known. Such a bearing apparatus generally includes a wheel speed detecting apparatus with a magnetic encoder having magnetic poles alternately arranged along its circumferential direction integrated into a sealing apparatus. The sealing apparatus is arranged between the inner and outer members to contain the rolling elements (balls or rollers). A wheel speed detecting sensor is present to detect the variation in the magnetic poles of the magnetic encoder according to the rotation of the wheel.
On the other hand, the wheel bearing apparatus to support a vehicle wheel has been orderly developed. In the first generation type, a double row rolling bearing is independently adopted provided with seals. In the second generation type, an outer member is integrally formed with a body mounting flange. In the third generation type, a wheel hub is integrally formed with a wheel mounting flange. Also, it is formed with one inner raceway surface of a double row rolling bearing on its outer circumferential surface. In the fourth generation type, a wheel hub is further combined with a constant velocity universal joint. The other inner raceway surface of the double row rolling bearing is formed on the outer circumferential surface of the outer joint member forming the constant velocity universal joint.
Recently, there is a tendency to adopt the fourth generation type to reduce weight and size in order to reduce manufacturing cost. In this case it is difficult to keep a space to mount the wheel speed detecting apparatus because of the integration of the constant velocity universal joint to the wheel hub. In such a wheel bearing apparatus, there is concern that foreign matter may become mingled with magnetic powder that would adhere to a magnetic encoder of the detecting portion of the wheel speed detecting apparatus. This is possible because the wheel speed detecting apparatus is exposed to muddy water and the foreign matters would contact the rotation speed detecting sensor and damage it or the magnetic encoder and thus detract from the detecting accuracy. A wheel bearing apparatus of the prior art which can solve such a problem is shown in FIG. 9.
The vehicle wheel bearing apparatus includes a constant velocity universal joint 51; a wheel hub 53 mounted on the outer circumference of a shaft portion 52 of the constant velocity universal joint 51; a double row rolling bearing 54 arranged both on the outer circumferences of the shaft portion 52 and the wheel hub 53; an inboard side seal 55 to seal the inboard side of the double row rolling bearing 54 arranged on the outer circumference of the constant velocity universal joint 51; and a wheel speed detecting apparatus 56 arranged on the outer circumference region at the inboard side of the double row rolling bearing 54. In the description of the present disclosure, an outer side of a bearing apparatus, when it is mounted on a vehicle, is referred to as the “outboard” side (the right side in FIG. 9), and an inner side of the bearing apparatus when it is mounted on a vehicle is referred to as the “inboard” side (the left side in FIG. 9).
The constant velocity universal joint 51 has a cup shaped outer joint member 57, a joint inner ring (not shown), torque transmitting balls, cage etc. The outer joint member 57 has a shaft portion 52 with splines 58 mating with splines of wheel hub 54. An outer circumferential surface of the outer joint member 57 is formed with an inner raceway surface 57a. In addition an annular recess 60 is formed between the outer joint member 57 and the shaft portion 52 opened toward the double row rolling bearing 54.
The wheel hub 53 has a hollow cylindrical configuration and is integrally formed with a radially extending wheel mounting flange 61. The hollow bore 62 of the wheel hub 53 is formed with splines 63. Another inner raceway surface 53a of the double row rolling bearing 54 is formed on the outer circumference of the wheel hub 53 at the inboard side of the wheel mounting flange 61.
The double row rolling bearing 54 is formed by a double row angular ball bearing. An outer member 59 is integrally formed with a body mounting flange 59b. Its inner circumference is formed with outer raceway surfaces 59a, 59a. An inner member 64 has double row inner raceway surfaces 53a, 57a on its outer circumference. The inner raceway surfaces 53a, 57a correspond to the double row outer raceway surfaces 59a, 59a. Double row balls 66 are contained between the double row inner and outer raceway surfaces, via cages 65. In the present specification, the inner member 64 includes the outer joint member 57 and the wheel hub 53. A seal 67 is arranged at the outboard side of the outer member 59.
The constant velocity universal joint 51, the wheel hub 53 and the double row rolling bearing 54 are assembled together by engaging splines of the wheel hub 53 and the constant velocity universal joint 51. The seal 67 and balls 66 are previously arranged on the outboard side between the outer member 59 and the wheel hub 53. Then the outboard side end of the shaft portion 52 is caulked on the outboard side end face of the wheel hub by bending the outboard side end of the shaft portion 52 radially outward.
The wheel speed detecting apparatus 56 includes a pulser ring 69 and a wheel speed sensor 70. The pulser ring 69 is formed as a disk. A permanent magnet is arranged on the disk. The magnet includes rubber magnet mingled with ferritic powder with N and S poles being alternately arranged along its circumferential direction. A supporting ring 71, having a L-shaped cross-section is press fit onto the shaft portion 52 of the constant velocity universal joint 51. The pulser ring 69 is secured on the supporting ring 71. A metal core 72, forming the inboard side seal 55 for the double row rolling bearing 54, axially extends to cover the annular recess 60.
A relatively long axial labyrinth gap S is formed between the metal core 72 and the outer joint member 57. The metal core 72 is formed with an elongated oval opening through which the wheel speed sensor 70 is inserted. The wheel speed sensor 70 is arranged opposite to the pulser ring 69 and is formed as an active sensor including a magnetic detecting element such as a Hall effect element or magnetic resistance element to vary output in accordance with the magnetic flow direction. IC etc is incorporated into a circuit to rectify the output wave form of the magnetic detecting element.
A knuckle 73, forming part of a suspension apparatus, is formed with a radially through bore 73a. The wheel speed sensor 70 is screwed into the bore 73a. Thus, the wheel rotation speed can be detected by the wheel speed sensor 70 detecting the variation of magnetic flux of the pulser ring 69 when the pulser ring is rotated in accordance with the rotation of the shaft portion 52 of the constant velocity universal joint 51.
As described above, due to the structure of the axially extending metal core 72 of the seal 55 in the double row rolling bearing 54, the wheel speed sensor 70 being passed through and screwed into the knuckle 73 and the annular recess 60 covered by the metal core 72, ingress of foreign matter, such as muddy water, into the annular recess 60 can be prevented.
Reference: Patent Document 1 (Japanese Laid-open Patent Publication No. 301854/2003).
However, since the detecting portion is merely covered by the labyrinth gap S between the metal core 72 and the outer joint member 57, it is insufficient to perfectly prevent the ingress of foreign matter, such as magnetic powder, although direct exposure to the detecting portion to muddy water can be prevented.
In addition, due to the structure of the wheel speed sensor 70 screwed into the knuckle 73 and passed through the opening of the metal core 72, it is difficult to firmly align the securing bore 73a of the knuckle 73 and the opening of the metal core 72. The number of machining processes of the bore or opening is increased and machining accuracy is required. This additionally increases the manufacturing cost of the wheel bearing apparatus.